In many wireless communication systems (e.g., a cellular communication system, a wireless local area network, etc.), a geographic area is divided into multiple wireless regions. In a cellular communication system, each cell (i.e., wireless region) is served by a fixed-location access point, which is commonly referred to in the industry as a base station, a Node B, a fixed station, and/or a cell tower. System users utilize mobile equipment to access communication services. Mobile equipment is commonly referred to the industry as user equipment (UE) devices, a mobile station (MS), and/or a mobile terminal (MT). Each cell is associated with a corresponding serving Node B. However, a Node B can serve multiple cells. To improve system performance, communication resources can be re-used across cells, where the re-use can be either “fractional re-use” or “full re-use.” These resources can include frequencies, time-slots, signature codes, channels, reference signals, etc. Wireless systems, which employ re-use of communications resources based on cellular boundaries, are commonly called cellular communication systems. Transmitters and receivers can be simultaneously present in any given cell. In case of uplink and/or reverse link communication, transmitters are at UE devices, and receivers are at Node Bs. In case of downlink and/or forward link communication, transmitters are at Node Bs, and receivers are at the UE devices.
Communication between transmitters and receivers occurs via signals. A signal can be designated as either a) an information-bearing signal, or b) a reference signal. Information-bearing signals may comprise data and/or control signals. Information-bearing signals carry information from the transmitter to the receiver. In contrast, a reference signal (RS) is a signal known a priori to both the transmitter and the receiver, and is therefore totally known by the receiver prior to any detection or estimation process. As such, a reference signal can be used for estimation of the characteristics of the communication medium (channel). A reference signal is sometimes also referred to as a pilot signal and/or a training signal. Reference signals may be used for: channel estimation, channel sounding for channel quality estimation, synchronization, timing-offset estimation, frequency-offset estimation, and/or as carriers when modulated (with data or control info). Channel estimates, which are obtained from received reference signals, are used for data demodulation. Channel quality indication (CQI) measurements, which may also obtained from received reference signals, can be used for purposes of user scheduling, link adaptation, interference coordination, handover, power control, and/or other purposes.
Channel-dependent scheduling is widely known to improve throughput and/or spectral efficiency in a wireless network by having the Node B assign an appropriate modulation and coding scheme for communication from and/or to a UE, depending on channel conditions, such as the received signal-to-interference and noise ratio (SINR), the UE experiences. In addition to channel-dependent time-domain scheduling, which assigns the data transmission in a time interval the UE experiences good SINR conditions, channel-dependent frequency-domain scheduling, which assigns the data transmission in a bandwidth portion the UE experiences good SINR conditions, has been shown to provide substantial gains over purely distributed and/or randomly localized (frequency hopped) scheduling in orthogonal frequency-division multiple-access (OFDMA)-based systems.